Contact lenses should be periodically cleaned and disinfected by the user to prevent infection or other deleterious effects on ocular health which may be associated with contact lens wear. Currently, there are several different conventional systems and methods which enable the user to clean and disinfect their contact lenses between wearing times. These conventional cleaning and disinfection systems can be divided into "hot" and "cold" systems. Hot systems require the use of heat to disinfect the contact lenses, whereas cold Systems use chemical disinfectants at ambient temperatures to disinfect the lenses.
Within the realm of cold disinfection systems are hydrogen peroxide disinfection systems. Disinfecting hydrogen peroxide solutions are effective to kill the bacteria and fungi which may contaminate contact lenses, however, residual hydrogen peroxide on a disinfected contact lens may cause irritation, burning or trauma to the eye unless this hydrogen peroxide is destroyed, i.e., decomposed, neutralized, inactivated or chemically reduced. Therefore, the destruction of the residua hydrogen peroxide in the liquid medium containing the disinfected contact lens is needed to enable safe and comfortable wear of the disinfected contact lens.
Contact lenses can be cleaned by enzymatic action. For example, Huth, et al U.S. Pat. No. RE. 32,677 discloses the simultaneous cleaning and disinfecting of contact lenses by a method which comprises contacting the lenses with a solution comprising a disinfecting amount of peroxide and an effective amount of peroxide-active proteolytic enzyme for a time sufficient to remove substantially all protein accretions and to disinfect the lenses. This patent further discloses that catalyze organic enzymes which catalyze the degradation of per-oxides, can be incorporated into tablets and powder, particularly in time-release form both the proteolytic enzyme and the catalyze should have high activity to provide a highly effective degree of cleaning and peroxide degradation, respectively.
Associated with the problem of hydrogen peroxide destruction in contact lens disinfection systems are the problems of easy use and user compliance. To enhance user compliance and ease of use, several efforts have focused on one-step disinfection and hydrogen peroxide destruction. In this regard, various time release tablets containing a core tablet and a totally soluble or insoluble coating have been suggested. Typical examples can be found in U.S. Pat. Nos. 4,568,517; 4,767,559; and 5,145,644.
The tablet having a barrier coating described in the above-mentioned prior art suffers the following disadvantages:
1. A complicated manufacturing process which requires a tableting procedure to form a naked tablet and a coating procedure for forming a barrier layer on the naked tablet; PA1 2. A relatively high manufacturing cost; and PA1 3. The tablet is vulnerable during manufacturing, transportation and storage so that pinholes and/or cracks are formed on the barrier coating, and thus the delayed release function is adversely affected or lost.
The primary objective of the present invention is to provide a hydrogen peroxide destroying composition which does not have the aforesaid drawbacks of the prior art.
A further objective of the present invention is to provide a hydrogen peroxide destroying composition which has a function of delayed releasing a hydrogen peroxide destroying component contained therein and a function of showing a sign of an initiation of neutralization of H.sub.2 O.sub.2 caused by the hydrogen peroxide destroying component.